Why we can't help eavesdropping on cellphone conversations

Can't help eavesdropping on that stranger's cellphone conversation?… (AFP )

Can you hear me now?

If you've ever been held captive in a bus or waiting room and been forced to endure a stranger's loud and astonishingly private cellphone conversation, you know how annoying secondhand phone chatter can be.

By the same token, you've probably been frustrated by your own inability to ignore the stranger's endless prattle. Like a bad song that gets stuck in your brain, details of the one-sided conversation can echo in your ears for hours afterward.

Well, with Americans logging some 2.3 trillion minutes worth of talk time on wireless devices each year, those overheard conversations aren't going away anytime soon. In fact, the phenomenon has become so prevalent that psychologists have begun to study the chatter's impact on the public.

In a study published Wednesday in the science journal PLoS One, researchers concluded that overheard one-sided cellphone conversations were more distracting and annoying than overheard conversations between two people talking face-to-face because they were inherently more "unpredictable."

With our brains constantly soaking up and evaluating information from our surrounding environment -- and dispensing with unneeded details -- one-sided conversations naturally captured our attention. Although people can tune out random noises, our brains essentially work double duty trying to figure out what the unheard portion of the conversation is.

Researchers based that conclusion on previous research, as well as an experiment performed on 149 University of San Diego undergrads. The students were led to believe they were participating in a study involving reading comprehension, and were asked to decipher a number of jumbled words, or anagrams.

Unbeknown to the test subjects, however, was the fact that other students in the room were in league with researchers. At a specific point in the experiment, these "confederate" students either began a scripted cellphone conversation alone, or started talking with a second confederate.

The seven-minute conversations covered three topics: a birthday present for dad, shopping for furniture, and meeting a date at a shopping mall. The test subjects were later asked about their reaction to the conversations and what they recalled.

"Participants who overheard the one-sided conversation were more surprised that the conversation took place, and rated the conversation as more noticeable and distracting than those who overheard the two-sided conversation," wrote Veronica Galvan, a neuroscientist and assistant professor at UCSD.

"They were also more likely to rate the content and volume of the conversation as annoying," Galvan and her colleagues wrote.

While the researchers anticipated that the one-sided conversation would be most disruptive, they said they were surprised to find that the background conversations failed to significantly affect the test subjects' ability to solve the assigned anagrams.

The researchers hypothesized that the anagrams were simple enough to allow the test subject's attention to wander to the confederate's conversations, but not difficult enough to result in increased mistakes.

Study authors said that while the distracting conversations did not cause subjects to make more mistakes, it was clear the brain was dividing its attention on the puzzle and the one-sided conversation.

"This study adds to the body of research by suggesting that overhearing a cellphone conversation competes for attentional resources that may have otherwise been devoted to other tasks," authors wrote.